Peripheral devices for connection to a data bus of a host system are widely known. Examples of such peripheral devices are external disk drives, printers or scanners that are connected to a host adapter of a computer system. In other fields of technology as well, however, peripheral devices are connected via data buses. Examples of these are consumer electronics or telecommunication electronic devices.
Many peripheral devices have a power supply of their own for supplying the peripheral device with an operating voltage. The result of this is that the peripheral devices generally continued to be supplied with energy even after a host system is switched off. Both the peripheral device itself and the power supply unit used for supplying the peripheral device cause power to be lost. This power loss generally consists to a large extent of losses from switching converters of the power supply unit.
DE 10 2007 052 880 discloses an electronic power supply unit that has a control unit which disconnects voltage-converting elements of a power supply from a primary-side AC voltage as a function of a power requirement of an electronic device connected thereto. Thus, the consumption of electric power in a standby state of the peripheral device can be largely avoided by the known circuit.
The solution according to prior art has the disadvantage, however, that under certain circumstances, an undesired deactivation of the peripheral device takes place when its power consumption declines, without a communication with the host system being interrupted. Under certain conditions, this leads to an error message in a host system connected to the peripheral device if the peripheral device is unexpectedly no longer accessible via a data bus. In addition, data losses can also occur in this case, particularly in the addressing of mass storage media.
It could therefore be helpful to provide an energy-saving circuit for a peripheral device for connection to a data bus of the host system, which circuit reduces power consumption of the peripheral device in a standby state without disrupting a communication of the data bus.
In addition, it could be helpful to provide a peripheral device, a switching device and an operating method that are suitable for use with the energy-saving circuit.